It’s easy to forget that “Guardians of the Galaxy” was the first big question mark for Marvel. After having great success with its earthbound heroes, the studio took its first big leap into the cosmic realm, anchoring it to a group of misfits that included a Walkman-wearing Earthling, a green-skinned assassin, a tattooed warrior, a badass raccoon and a sentient tree named Groot. It was easy to see this as a possible bridge too far for mainstream audiences, especially since the Guardians were at best a third-tier team in the Marvel Comics pantheon.

But the film was one of the studio’s biggest successes, bringing in nearly $1 billion worldwide. Audiences loved James Gunn’s mix of galactic action and strange humor, set to a soundtrack of 70s rock. Critics responded to the lavish visuals and roguish protagonists (I had the film on my top ten list for 2014). While only tangentially related to the bigger Marvel empire, “Guardians” was crucial in opening the studio’s universe to cosmic — and eventually mystical — realms and telling stories with a unique directorial vision.

So it’s inevitable that the Guardians are blasting into theaters once more. And while it’s impossible for “Guardians of the Galaxy Vol. 2” to recapture the freshness and surprise of the original, hanging out with this team is still a blast.

Any worries that Gunn couldn’t recapture the first film’s offbeat tone are put to rest by the time the opening credits finish. As the ensemble tussles with an otherworldly monster in the background, an infant version of Groot wiggles and bebops to ELO’s “Mr. Blue Sky.” It’s an adorable return to the quirkiest corner of the Marvel Cinematic Universe, and an assurance that Gunn hasn’t let blockbuster success rob him — or his heroes — of weirdness. Five minutes in and a smile was on my face that didn’t leave until the final post-credit scene.

Daddy issues and old frenemies

“Guardians of the Galaxy Vol. 2” (GOTG2 from here on out) takes place a few months after the previous film and finds the team as galactic heroes for hire. After Rocket Raccoon (Bradley Cooper) swipes some priceless batteries from a race of golden-skinned Sovereigns, they find themselves pursued by vicious Ravagers and stranded on a mysterious planet. There, a bearded man named Ego appears and tells Peter Quill (Chris Pratt) that he’s his father. It’s not too hard to believe. Not only is Ego the only other human around for light years, but he’s also played by Kurt Russell, the swaggering ’80s icon who’s perhaps the perfect person to have fathered the preening Star Lord (well, that and David Hasselhoff, who gets several shout outs).

Quill, Gamora (Zoe Saldana) and Drax (Dave Bautista) head off to Ego’s planet, which contains not only the mysterious and empathetic Mantis (Pom Klementieff) but its own deep secrets that cut to the core of Star Lord’s identity. Meanwhile, Rocket and Groot stay back to repair their damaged ship and keep an eye on Nebula (Karen Gillian), Gamora’s villainous cyborg sister, who they’re taking back for imprisonment. The trio is set upon by Quill’s surrogate father Yondu (Michael Rooker), the Ravager who raised Peter and has become an outcast for his actions.

That’s about the first half-hour of the film and it’s there that I’ll end with the plot descriptions. Where too many Marvel movies have been (rightly) criticized for their reliance on plots where heroes and villains pursue powerful glowing objects, GOTG2 offers a refreshing break from formula. Last year’s “Captain America: Civil War” proved that Marvel’s universe was strong enough to sustain a story that didn’t need magic MacGuffins or supervillains so long as each adventure was rooted in character. While the studio dipped back into routine for “Doctor Strange,” the colorful ensemble at the core of “Guardians of the Galaxy” allows Gunn to tell a story that unfolds organically from the characters and gives each their own emotional arc, with results that are frequently funny and occasionally moving.

And so you have Quill wrestling with his parentage while Gamora struggles with whether to reconcile with a sister who might want to kill her. The hyper-literal Drax bonds with the emotional and empathetic Mantis, forming a pseudo father-daughter bond that is as touching as it is funny. Prickly Rocket and Yondu find they have more in common than a love of combat and a hatred of a beast named Taserface. And Groot, returned to sapling form at the end of the first film, scampers about looking precious (I imagine stuffed Baby Groots will be a popular item this Christmas season).

The plot might be overstuffed and under-focused, but I’ll take a messy story that springs from character over an efficient, by-the-numbers slog any day. And it helps that Marvel’s penchant for casting hit its apex with “Guardians.” Former wrestler Bautista walks away with the film’s biggest non-Groot laughs this time out, and Russell brings an entire planet’s worth of charisma to his role as Peter’s cad dad. Saldana and Gillian find notes of sisterly love to root their tempestuous relationship, and Rooker sinks his teeth into a deeper, emotionally complex story for Yondu. Computer technology makes Rocket and Groot feel less like effects and more like three-dimensional characters, helped along by charming voice work from Cooper and Vin Diesel, who milks humor and nuance out of the only three words Groot knows. Pratt is largely relegated to the role of straight man, and while it’s a shame that his charisma and humor are reined in, the actor nails some emotional high points late in the film.

About 15 minutes into the movie, after the Guardians have vanquished a snarling beast and Rocket’s absconded with the Sovereigns’ batteries, I smiled. I realized I’d missed these guys; I was happy just to spend time hanging out with them. I didn’t know what was going to happen next, and the story wasn’t laying out easy-to-call beats. Tucked away in its own corner of the Marvel universe, with no tie-ins to the Avengers (for now), Gunn’s able to deepen these characters’ relationships and weave an adventure that embraces some of the weirder concepts in Marvel’s cosmic universe. And he has a fantastic sandbox to play in.

Visual marvel and space oddity

The Marvel movies are often derided for having an uninspired visual palette, a consequence of trying to create a coherent tone across several different franchises. But like its predecessor, GOTG2 stands out not only from the other Marvel films but a plethora of gunmetal-gray blockbusters by bursting with colorful images that pop off the screen (and look fantastic in 3D).

Gunn delivers an entry that is by turns kaleidoscopic and surreal. Characters sear into our eyes with green, blue, purple and yellow skin. Spaceships straight out of 1950s sci-fi zip and tumble through the cosmos and interplanetary landscapes that look ripped from the cover of 1970s rock albums. There’s a gorgeous slow motion battle that pits Yondu, Groot and Rocket against a ship of ravagers; a psychedelic blast through 700 wormholes; and a climax in which the heroes battle a planet that is literally alive. Despite being a sequel, GOTG2 feels fresh with imagination in a way few blockbusters are. Given the keys to do whatever he wants, Gunn brings to life a thrilling, energetic and deeply weird film.

He also keeps his quirky sensibilities intact. A twisted sense of humor has been the director’s calling card since his Troma days, and billion-dollar success hasn’t turned him pretentious. Despite thrilling adventure and amazing visuals, this is still a movie that opens with a discussion of Drax’s sensitive nipples and has an argument where two superheroes argue about leaving turds in each other’s pillowcases, not to mention questions about whether a god who turned himself human has also fashioned himself a penis (for the record: he did and proclaims “it’s not half-bad.”) Bautista’s Drax, who never speaks in metaphors, gets several of the film’s funniest lines, but he’s matched by sarcastic outbursts from Rocket, whose prickly demeanor belies loyalty and care for his friends. All of this is, once again, underscored by a soundtrack of ’70s rock hits. It’s a movie that opens with a dance sequence set to “Mr. Blue Sky” and uses “Brandy” by Looking Glass as a touchpoint for character bonding.

It’s sometimes hard to believe that Marvel’s been building this bizarre, interconnected universe for less than a decade. What started with a simple story about a superhero in metal armor is now a sprawling, multi-character empire that spans galaxies and spiritual dimensions. But the “Guardians of the Galaxy” films have always occupied a funny, thrilling corner of the Marvel universe that plays by its own weird rules. “Guardians of the Galaxy Vol. 2” could be criticized as being more of the same, but I don’t really think that’s fair. Yes, it returns to similar jokes and beats, but does so with more depth and a story that breaks free of the studio’s traditional mold. It’s not just one of the best films in the Marvel Cinematic Universe; it sets the bar for this summer’s movies high enough that I’m not sure any other films are capable of clearing it.